I am running Excalibur and just ran an update.  Everything updated
except for 28 packages, all of which are libvirt packages.  My VM does
not run, now.  I start libvirt manager, select the VM, and try to start
it.  I get an error saying:

    Error starting domain: Requested operation is not valid: network
'default' is not active

I assume that there is something that needs to be done after a new
kernel is installed, but assumptions are always dangerous.  I am using
QEMU/KVM.  Can anyone tell me what I need to do to fix this?  Do I just
need to manually update those libvirt packages? Or is there something
else that I need to do first, or afterward?

Marc